When it is necessary to fasten two elements together, as a pair of metal plates or a metal plate and a supporting bar, it is standard practice to use a simple screw and nut. Such an arrangement allows the tool elements to be secured together with considerable force, yet nonetheless usually allows subsequent disassembly. The disadvantage of this type of arrangement is that the screw and nut are relatively expensive, and once badly corroded it is often very difficult to open up such a fastener. What is more it is necessary normally to use a pair of separate tools, commonly a screwdriver or allen key and a wrench of some type, to install such a fastener.
It is also known to rivet together a pair of elements. Such a system has the advantage that a rivet is normally a very inexpensive item. Nonetheless even more elaborate tools are needed for riveting than for securing a screw-and-nut fastener. In addition subsequent removal of a rivet is often extremely difficult, requiring laborious drilling-out of the rivet or grinding-off of its head.
It is also known, in particular on farm equipment, to secure elements together by means of a bolt having a stem extending through aligned holes in the elements to be joined, a head to one side of the elements, and a transversely throughgoing bore to the other side of these elements. A cotter pin is passed through this transversely throughgoing bore after the bolt has been pushed through the elements, and this cotter pin is then bent over. Such an arrangement can be made at relatively low cost, and can even be unfastened relatively easily by merely straightening out or cutting off the inexpensive cotter pin. Nonetheless such a system has the enormous disadvantage that it can not secure two elements tightly together, but can only be used in arrangements where considerable play is permissible between the elements being secured together.